Box flapper

ABSTRACT

A box flapper positions a transverse flap on each of a succession of boxes that are spaced apart and have their main side flaps fully opened. It uses a horizontally rotatable arm alongside the path of travel of the boxes and driven by a motor through a solenoid-controlled clutch and brake to rotate rapidly in 90* arcs in time with the boxes for either opening or closing a transverse flap.

United States Patent [1 1 Peres Jan. 21, 1975 {5 BOX FLAPPER 3,662,5165/1972 Wiseman 53/76 [75] Inventor: Anthony R. Peres, Bristol, NY.Primary Examiner Travis S McGehee [73] Assignee: Press ElectronicMachines, Inc., Attorney, Agent, or FirmCumpston, Shaw &

Bristol, N.Y. Stephens [22] Filed: Jan. 23, 1974 [57] ABSTRACT [21]Appl' 435880 A box flapper positions a transverse flap on each of asuccession of boxes that are spaced apart and have [52] US. Cl 53/76,53/374, 53/382 their main si flaps fully opened. It uses a horizon- [51]Int. Cl B65b 57/02, B65b 43/39 tally rotatable arm alongside the path oftravel of the [58] Field of Search 53/76, 382 boxes and driven by amotor through a solenoidcontrolled clutch and brake to rotate rapidly in90 {56] References Cited arcs in time with the boxes for either openingor clos- UNITED STATES PATENTS mg a transverse 3,296,769 1/1967 Patton53/76 21 Claims, 18 Drawing Figures PATENTED JANZ 1 I975 SHEET 2 OF 4PATENTEB JAN 2 1 I975 SHEEI 30F 4 PATENTED 3,861,115

sIIEEI nor 4 FIG. I?

LEADING END TRAILING END OPENS CLOSES PHOTOCELL PHOTOCELL CIRCUIT 43CIRCUIT TIME 1 7 44 I\fzw ADJUSTABLE ADJUSTABLE DELAY 45 r D Y -45 I I II AIR soLENoID 33 AIR SOLENOID CYLI CONTROLLED CYLINDER CONTROLLEDCLUTCH a CLUTCH a BRAKE I BRAKE I I GATE RAIsEs ARM ACTUATES GATE LOWERSARM DELAYS To WIRED & RAE: SU zICEEDING BOX FLAP STOP BOX BEH'ND RETuRNsT o R ST SUCCEEDING BOX AIR LINE AIR LINE soLENoID 4e sc LENc Io ,46

OPENS L03 3 F IG. 8

BOX FLAPPER THE INVENTIVE IMPROVEMENT Box flappers for positioningtransverse flaps on boxes have used rack and pinion operated arms drivenin reciprocal motions to swing into engagement with a transverse flapand then move out of the way of a succeeding box. Such mechanisms areslow, cumbersome, and require frequent repairs.

The invention involves a realization of a way to make a box flapper thatoperates faster and more reliably, allows faster box speeds past theflapper and requires less maintenance. The invention aims at a boxflapper that is versatile, reliable, economical, and efficient.

SUMMARY OF THE INVENTION The inventive box flapper positions atransverse flap on each of a succession of boxes that are spaced apartand have their main side flaps fully open as they move through aflapping region. A horizontally rotatable arm having flap engaging meanson each end is arranged alongside the path of travel of the boxesthrough the flapping region, and the arm has a rest positionapproximately parallel with the path and an operating positiontransverse to the path. A motor rotatably drives the arms through asolenoid-controlled clutch and brake, and the approach of a transverseflap on one of the boxes is detected for rotating the arm approximately90 in an arc curving in the general direction of motion of the box tothe transverse position of the arm where the flap engaging means on thearm overtakes, engages and positions the flap. Then thesolenoid-controlled clutch and brake operates after the positioning ofthe flap to rotate the arm approximately 90 in an arc in the generaldirection of movement of the box to returnthe arm to the rest position.The invention can be used for closing the trailing transverse flap of asuccession of boxes or for opening both the leading and trailing flapsof the succession of boxes.

DRAWINGS FIGS. 1-3 are partially schematic, side elevational views of abox having both its transverse flaps opened as it proceeds through apreferred embodiment of the inventive flapper;

FIGS. 4-6 are partially schematic, plan views of a box proceedingthrough the flapper of FIGS. 1-3;

FIGS. 7 and 8 are partially schematic, side elevational views of a boxhaving its transverse flaps closed as it proceeds through anotherembodiment of the inventive flapper;

FIGS. 9 and 10 are partially schematic, plan views of a box proceedingthrough the flapper of FIGS. 7 and 8;

FIGS. 11-14 are partially schematic, plan views of the operation of abox separating device cooperating with the inventive flapper;

FIG. 15 is a partially schematic, plan view of a preferred embodiment ofa box separating device;

FIG. 16 is a partially schematic, perspective view of the box separatingdevice in FIG. 17;

FIG. 17 is a side elevational view of a preferred embodiment of aportion of the inventive flapper; and

FIG. 18 is a schematic diagram of the time relationship of events in apreferred embodiment of the inventive flapper.

DETAILED DESCRIPTION The inventive box flapper can either open thetransverse flaps of a box as shown schematically in FIGS. 1-6 or closethe transverse flaps of a box as shown schematically in FIGS. 7-10, andin either case, the main side flaps are spread fully open in generallyknown ways. Also, the boxes are spaced apart as they proceed through aflapping region, and the flapping is generally accomplished by arotatable arm 10. Arm [0 has rollers 12 for engaging the transverseflaps 13 and 14 of a box 15, and guide bars 11 plow open the main sideflaps 16 of the box 15 in a generally known way. Box 15 is carriedthrough a flapping region adjacent to arm 10 by a flapper conveyor 17moving relatively fast to advance box 15 faster thana supply conveyor.

Beginning with FIG. 1, box 15 is approaching a flapping region adjacentarm 10 and is moved along by conveyor 17 with its main side flap 16open, and its transverse flaps l3 and 14 extending upward from box 15.When box 15 reaches the position of FIG.- 2, arm 10 rotates rapidly tomove roller 12 into engagement with flap 13 to pivot flap 13 forward ofbox 15 where it is held down by a guide bar 18. In such a position, arm10 is transverse to the path of box 15 and extending over the top of box15 as illustrated, and arm 10 stays in this position while box 15advances to the position of FIG. 3 where a trailing roller 12 on arm 10engages flap 14 to bend flap 14 rearward of box 15 so it will pass underguide bar 18 and be held down.

This process opens all four flaps of box 15 so that box 15 can be loadedwith items, and the above-described operation is illustrated in planview and FIGS. 4-6.

In a similar operation, the inventive flapper can close the transverseflaps of box 15 for sealing box 15 closed after it is loaded. Main sideflaps 16 are again plowed open in the usual way by guide bars 11, andleading transverse flap 13 is forced down by guide bar 18 as box 15 isadvanced through a flapping region adjacent arm 10 by flapper conveyor17 as shown in FIG. 7. When trailing flap 14 moves to the properposition, arm 10 rotates rapidly to bring wheel 12 into engagement withflap 14 to bend flap l4 forward so that it will move under guide bar 18and be held closed. Then main side flaps 16 are swung closed to seal box15, and the abovedescribed process is schematically illustrated in planview in FIGS. 9 and 10. Arm 10 need only have leading rollers 12 anddoes not require any trailing rollers 12 when it is operated as shown inFIGS. 7-10 only for closing a trailing flap 14.

Boxes are preferably spaced apart as they move through a flappingregion, and a preferred way of spacing the boxes is schematicallyillustrated in FIGS. 11-14. Flapper conveyor 17, as previouslydescribed, carries the boxes rapidly'through a flapping region andsupply conveyor 19 delivers a succession of boxes having letteridentifications in FIGS. 11-14. For simplicity of illustration, flapsare not shown on the boxes of FIGS. 11-14.

A gate 20 is positioned between conveyors 1'7 and 19 to be inserted intothe path of the boxes or withdrawn from the path of the boxes desired.Gate 20 preferably moves up and down, and is described in greater detailbelow. Box separating arms 21 move pivotally in and out alongside therow of boxes in synchronization with gate 20, and arms 21 carry springloaded wedges 22 for separating boxes. When gate 20 is up, as shown inFIG.

l1, arms 21 are separated, and when gate 20 lowers to let a box pass,arms 21 close as shown in FIG. 12.

Beginning with gate 20 up, as shown in FIG. 11, the boxes on conveyor 19are stopped and a sequence of events is ready to begin. When gate 20lowers, as shown in FlG. 12, box A advances onto flapper conveyor 17 andaccelerates away from box B which moves along on the slower feedconveyor 19. Lowering of gate 20 also pivots arms 21 inward so thatwedges 22 spring in behind the trailing edge of box B and stop theleading edge of box C. Box B then moves toward gate 20 as box A movesthrough the flapping region. As box A enters the flapping region, asshown in FIG. 13, gate 20 raises behind box A and box separator arms 21open to let box C advance. When box A completes its pass through theflapping region, as shown in FIG. 14, gate 20 lowers to let box B passand separator arm 21 close against the side of box C to move in past thetrailing edge of box C and stop box D. The sequence of events is timedso that for continuous operation, gate 20 lowers before a box reaches itwithout stopping boxes, because preceding boxes have moved rapidlyenough through the flapping region. If there is any delay or accident,however, gate 20 stops the boxes on conveyor 19 to keep them fromrunning onto flapper conveyor 17.

The preferred box separating mechanism is shown in more detail in FIGS.and 16. Gate has a cam shape and is raised and lowered by a pneumaticcylinder 23 in time with the machine. A pair of follower rollers 24 rideon the sides of gate cams 20 and move the ends 25 of arms 21 which arepivoted in supports 26 for pivotal motion in synchronization with gate20 as described above. Wedges 22 are mounted in housings 28 and biasedoutward toward boxes by springs 27. Then when arms 21 pivot inward,wedges 22 engage the opposite sides of a box and are depressed intohousings 28 to compress springs 27 When the trailing edge of a boxpasses by wedges 22, they spring inward under the bias of springs 27 tostop the leading edge of a succeeding box. The operation of air cylinder23 is timed with the flapping machine as described below, and the timingelement preferably includes aphotocell circuit including a light source29 and a receiver 30 arranged across the path of travel of the boxes.

Arm 10 is supportedon a shaft 31 and driven by a motor 32 through asolenoid-controlled clutch and brake 33 and a gear box 34.Solenoid-controlled-clutch and brake 33 is a fast-acting, electricallycontrolled device for either releasing a brake and engaging a clutch ina drive train between motor 32 and arm 10, or disengaging the drivetrain and engaging the brake to stop arm 10, and meanwhile, motor 32operates continuously so that power can be quickly applied for rotatingarm 10 and quickly shut off for stopping arm 10.

Motor 32, solenoid-controlled clutch and brake 33, and gear box 34 aremounted on a support plate 35, and shaft 31 and arm 10 are supported ona bracket 36 below plate alongside the flapping region. Arm 10 has apair of leading rollers 12 for overtaking and engaging a flap as arm 10rotates in the forward direction and a trailing roller 12 for engaging atrailing flap passing under arm 10. A micro switch 37 is positioned toengage an end of arm 10 when arm 10 is in a transverse operatingposition as illustrated in FIG. 17 for stopping arm 10 in suchtransverse position by disengaging the clutch and applying the brake ofsolenoid-controlled clutch and brake 33. Another micro switch 38 ispositioned to engage an end of arm l0'to stop arm 10 in. a rest positionby disengaging the clutch and engaging the brake of solenoid-controlledclutch and brake 33. A signal timed with the movement of boxes throughthe flapping region starts arm 10 in motion by engaging the clutch andreleasing the brake of solenoid-controlled clutch and brake 33, and suchmotion is stopped by engagement of arm 10 with one of the micro switches37 or 38. i

To aid in opening or closing transverse flaps, air nozzles 39 arearranged between leading rollersl2 and are fed with air supplied throughan air inlet 41, a rotatable union 42, and air lines 40. Nozzles 39 areaimed to direct an air blast up under the bottom surface of a leadingflap to raise the flap enough for secure engagement by rollers 12. Airis preferably supplied to inlet 41b opening a solenoid valve only whenarm 10 rotates into the transverse operating position to conserve airand reduce noise so that no air is delivered when arm 10 is in a-restposition. Also, in many flapping operations, air nozzles 39 are notrequired.

The timing of the operations of the inventive flapper is best shownschematically in FIG. 18 relative to an advancing time line 43. Timingis preferably accomplished through the photocell circuit of sensor 29and receiver 30 as shown in FIG. 15, and FIG. '3 illustrates theoperations for opening both the leading and trailing flaps of a box.

The opening or interrupting of the photocell circuit by the leading endof a box at point 44 is used for timing several operations. Thephotocell circuit preferably includes an adjustable delay 45 that canvary the timing of events after interruption of the photocell circuit orafter reclosure of the photocell circuit as desired. This allows thetiming of the flapper to be adjusted without physically moving thephotocell circuit. Then adjustable delay 45 is properly set to, operateair cylinder 23 to start raising gate 20 behind the box that interruptedthe photocell circuit to stop the next box and release the succeedingbox. Also, solenoid-controlled clutch and brake 33 is operated to rotatearm 10 into a transverse operating position to openthe leading flap ofthe box. If air nozzles are used next to rollers 12 to assist in this,air line solenoid 46 is opened at this time. Arm

10 then stays in the operating position as the box moves under arm 10and time elapses along line 43.

When'the trailing end of the boxpasses beyond the photocell circuit toreclose the circuit at point 47, adjustable delay 45 times several otherevents. Air cylinder 23 is operated to lower gate 20 to release the nextbox to advance onto the flapper conveyor and to stop the box behind thesucceeding box which proceeds toward the gate. At the same time, thesolenoidcontrolled clutch and brake is operated to move the flapper armback to its rest position, and if air nozzles are used, the air line tothe nozzles is closed by operation of solenoid 46. I v

if the inventive flapper is used only for closing a trailing flap of abox, the operation can be adjustably timed by the reclosure of thephotocell circuit by passage of the trailing end of the box past thephotocell circuit. instead of microswitches 37 and 38, as previouslydescribed for stopping arm 10 in a desired position, arm 10 can beoperated on signal for a predetermined interval and then stoppedautomatically by expiration of the interval. Timing signals can beproduced by devices other than a photocell circuit, and other mechanismscan be used for separating the boxes as they proceed through a flappingregion. There are also many timing,

control, and valve operating devices that can be used with the inventionas will be apparent to those skilled in the art.

The use of a continuously driven motor 32 selectively coupled to theflapper arm by a solenoid-controlled clutch and brake 33 allows rapidand accurate operation of arm which can swing quickly through a 90 arcto overtake and open or close a transverse flap accurately, even thoughthe box may be moving relatively fast through the flapper region. Thequick, successive 90 rotations of arm 10 allow higher speed box travel,insure accurate flapping of the box, and are accomplished with littlewear or requirements for maintenance. Hence, the inventive flapper isfast, efficient, reliable, and trouble-free.

Persons wishing to practice the invention should remember that otherembodiments and variations can be adapted to particular circumstances.Even though one point of view is necessarily chosen in describing anddefining the invention, this should not inhibit broader or relatedembodiments going beyond the semantic orientation of this applicationbut falling within the spiritof the invention. For example, thoseskilled in the art will appreciate the many control systems, box spacingmechanisms, and other devices that can be used with the inventiveflapper to fit various circumstances.

I claim:

1. A box flapper for positioning a transverse flap on each of asuccession of boxes, said box flapper comprismg:

a. means for spacing said boxes apart as said boxes move through aflapping region;

b. means for fully opening the main side flaps of said boxes as saidboxes move through said flapping region;

c. a horizontally rotatable arm arranged alongside the path of travel ofsaid boxes through said flapping region;

d. said arm having a rest position approximately parallel with said pathand an operating position transverse to said path;

e. each end of said arm having flap engaging means;

f. a motor;

g. a solenoid-controlled clutch and brake driven by said motor andselectively transmitting said motor drive to said arm;

h. means for detecting the approach of said transverse flap of one ofsaid boxes to said flapping region;

means responsive to said approach detecting means for operating saidsolenoid-controlled clutch and brake to rotate said arm approximately 90in an arc curving in the general direction of motion of said one box tosaid transverse position of said arm where said flap engaging means ofsaid arm overtakes, engages, and positions said transverse flap of saidone box; and j. means for operating said solenoid-controlled clutch andbrake after said positioning of said transverse flap to rotate said armapproximately 90 in an arc in the general direction of movement of saidone box to return said arm to said rest position.

2. The box flapper of claim 1 including a first micro switch engageableby said arm in said transverse position for operating saidsolenoid-controlled clutch and brake to stop each rotation of said armat said transverse position, and a second micro switch engageable bysaid arm in said rest position for operating said solenoid-controlledclutch and brake to stop said rotation of said arm at said restposition.

3. The box flapper of claim 1 wherein said flap engaging means comprisesrollers on each end of said arm.

4. The box flapper of claim 1 including air nozzles arranged for blowingair to raise said flap for reliable engagement by said flap engagingmeans.

5. The box flapper of claim 1 including a box supply conveyor and aflapper conveyor receiving boxes from said box supply conveyor andmoving substantially- 7. The box flapper of claim 1 including delaymeans for operating said arm returning means a predetermined intervalafter rotating said arm to said transverse position.

8. The box flapper of claim 1 wherein said transverse flap is a leadingflap of said one box, said approach detecting means detects the approachof the leading end of said one box, actuation of said arm opens saidleading transverse flap of said one box, and including means for holdingsaid arm in said transverse position to open a trailing transverse flapof said one box.

9. The box flapper of claim 8 including means for de tecting the exit ofsaid one box from said flapping region, and said arm return means beingresponsive to said exit detecting means.

10. The box flapper of claim 9 including a photoelectric circuit acrosssaid box path, said photoelectric circuit being arranged so that saidapproach detection occurs on interruption of said photoelectric circuitby said leading end of said one box, and said exit detecting occurs onrestoration of said photoelectric circuit by the passing of the trailingend of said one box.

11. The box flapper of claim 8 wherein said flap engaging means includesboth leading and trailing rollers oriented on each end of said armrelative to the direction of rotation of said arm so that leadingrollers engage and open said leading transverse flap of said one box andtrailing rollers engage and open said trailing transverse flap of saidone box.

12. The box flapper of claim 11 including a first micro switchengageable by said arm in said transverse position for operating saidsolenoid-controlled clutch and brake to stop said rotation of said armat said trans verse position, and a second micro switch engageable bysaid arm in said rest position for operating said solenoid-controlledclutch and brake to stop said rotation of said arm at said restposition.

13. The box flapper of claim 12 including means for detecting the exitof said one box from said flapping region, and said arm return meansbeing responsive to said exit detecting means, and including aphotoelectric circuit across said box path, said photoelectric circuitbeing arranged so that said approach detection occurs on interruption ofsaid photoelectric circuit by said leading end of said one box, and saidexit detecting occurs on restoration of said photoelectric circuit bythe passing of the trailing end of said one box.

14. The box flapper of claim 13 including air nozzles arranged forblowing air to raise said flap for reliable engagement by said flapengaging means.

15. The box flapper of claim 14 including an air line supplying air tosaid nozzles, a solenoid-controlled valve in said air line, and meansfor opening said solenoid-controlled valve in response to said approachdetecting means and for closing said solenoid-controlled valve inresponse to said exit detecting means.

16. The box flapper of claim including a box supply conveyor and aflapper conveyor receiving boxes from said box supply conveyor andmoving substantially faster than said box supply conveyor for movingsaid boxes through said flapping region, and wherein said box spacingmeans includes a gate moveable into and out of said box path.

17. Thebox flapper of claim 16 including means operable with said gatefor stopping a box following a succeeding one of said boxes proceedingbehind said one box when said gate moves from said box path to admitsaid one box into said flapping region.

18. The box flapper of claim 17 including means responsive to saidapproach detecting means for moving said gate into said box path behindsaid one box and ahead of said succeeding box, said box stopping meansbeing deactivated to release said following box upon movement of saidgate into said box path ahead of said succeeding box.

19. The box flapper of claim 18 including means responsive to said exitdetecting means for moving said gate from said box path and operatingsaid box stopping means, and wherein said gate includes cam means, andfollower means engaging said cam means operates said box stopping means.

20. The box flapper of claim 19 wherein said box stopping means includesa pair of spring-loaded wedges engaging and riding along opposite sidesof said succeeding box and for springing inward to stop said followingbox when the trailing end of said succeeding box moves past said wedgemeans.

21. The box flapper of claim 20 wherein said flap engaging meansincludes both leading and trailing rollers oriented on each end of saidarm relative to the direction of rotation of said arm so that leadingrollers engage and open said leading transverse flap of said one box andtrailing rollers engage and open said trailing transverse flap of saidone box.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 3 1115 Dated January 21, 1225 In t r-( Anthony R. Peres It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

The name of the assignee should read Peres Electronic Machines, Inc.

Signed sealed this 15th of April L375.

F ORM PO-105O (10-9) USCOMM-DC 60375-P69 l.l.5 GOVERNMENT PRINUNOOFFICE: 8 6 9- 9 o

1. A box flappeR for positioning a transverse flap on each of asuccession of boxes, said box flapper comprising: a. means for spacingsaid boxes apart as said boxes move through a flapping region; b. meansfor fully opening the main side flaps of said boxes as said boxes movethrough said flapping region; c. a horizontally rotatable arm arrangedalongside the path of travel of said boxes through said flapping region;d. said arm having a rest position approximately parallel with said pathand an operating position transverse to said path; e. each end of saidarm having flap engaging means; f. a motor; g. a solenoid-controlledclutch and brake driven by said motor and selectively transmitting saidmotor drive to said arm; h. means for detecting the approach of saidtransverse flap of one of said boxes to said flapping region; i. meansresponsive to said approach detecting means for operating saidsolenoid-controlled clutch and brake to rotate said arm approximately90* in an arc curving in the general direction of motion of said one boxto said transverse position of said arm where said flap engaging meansof said arm overtakes, engages, and positions said transverse flap ofsaid one box; and j. means for operating said solenoid-controlled clutchand brake after said positioning of said transverse flap to rotate saidarm approximately 90* in an arc in the general direction of movement ofsaid one box to return said arm to said rest position.
 2. The boxflapper of claim 1 including a first micro switch engageable by said armin said transverse position for operating said solenoid-controlledclutch and brake to stop each rotation of said arm at said transverseposition, and a second micro switch engageable by said arm in said restposition for operating said solenoid-controlled clutch and brake to stopsaid rotation of said arm at said rest position.
 3. The box flapper ofclaim 1 wherein said flap engaging means comprises rollers on each endof said arm.
 4. The box flapper of claim 1 including air nozzlesarranged for blowing air to raise said flap for reliable engagement bysaid flap engaging means.
 5. The box flapper of claim 1 including a boxsupply conveyor and a flapper conveyor receiving boxes from said boxsupply conveyor and moving substantially faster than said box supplyconveyor for moving said boxes through said flapping region.
 6. The boxflapper of claim 1 wherein said box spacing means includes a gatemoveable into and out of said box path.
 7. The box flapper of claim 1including delay means for operating said arm returning means apredetermined interval after rotating said arm to said transverseposition.
 8. The box flapper of claim 1 wherein said transverse flap isa leading flap of said one box, said approach detecting means detectsthe approach of the leading end of said one box, actuation of said armopens said leading transverse flap of said one box, and including meansfor holding said arm in said transverse position to open a trailingtransverse flap of said one box.
 9. The box flapper of claim 8 includingmeans for detecting the exit of said one box from said flapping region,and said arm return means being responsive to said exit detecting means.10. The box flapper of claim 9 including a photoelectric circuit acrosssaid box path, said photoelectric circuit being arranged so that saidapproach detection occurs on interruption of said photoelectric circuitby said leading end of said one box, and said exit detecting occurs onrestoration of said photoelectric circuit by the passing of the trailingend of said one box.
 11. The box flapper of claim 8 wherein said flapengaging means includes both leading and trailing rollers oriented oneach end of said arm relative to the direction of rotation of said armso that leading rollers engage and open said leading transverse flap ofsaid one box and trailing rollers engage and open said trailingtransverse flap of said one box.
 12. The box flapper of claim 11including a first micro switch engageable by said arm in said transverseposition for operating said solenoid-controlled clutch and brake to stopsaid rotation of said arm at said transverse position, and a secondmicro switch engageable by said arm in said rest position for operatingsaid solenoid-controlled clutch and brake to stop said rotation of saidarm at said rest position.
 13. The box flapper of claim 12 includingmeans for detecting the exit of said one box from said flapping region,and said arm return means being responsive to said exit detecting means,and including a photoelectric circuit across said box path, saidphotoelectric circuit being arranged so that said approach detectionoccurs on interruption of said photoelectric circuit by said leading endof said one box, and said exit detecting occurs on restoration of saidphotoelectric circuit by the passing of the trailing end of said onebox.
 14. The box flapper of claim 13 including air nozzles arranged forblowing air to raise said flap for reliable engagement by said flapengaging means.
 15. The box flapper of claim 14 including an air linesupplying air to said nozzles, a solenoid-controlled valve in said airline, and means for opening said solenoid-controlled valve in responseto said approach detecting means and for closing saidsolenoid-controlled valve in response to said exit detecting means. 16.The box flapper of claim 10 including a box supply conveyor and aflapper conveyor receiving boxes from said box supply conveyor andmoving substantially faster than said box supply conveyor for movingsaid boxes through said flapping region, and wherein said box spacingmeans includes a gate moveable into and out of said box path.
 17. Thebox flapper of claim 16 including means operable with said gate forstopping a box following a succeeding one of said boxes proceedingbehind said one box when said gate moves from said box path to admitsaid one box into said flapping region.
 18. The box flapper of claim 17including means responsive to said approach detecting means for movingsaid gate into said box path behind said one box and ahead of saidsucceeding box, said box stopping means being deactivated to releasesaid following box upon movement of said gate into said box path aheadof said succeeding box.
 19. The box flapper of claim 18 including meansresponsive to said exit detecting means for moving said gate from saidbox path and operating said box stopping means, and wherein said gateincludes cam means, and follower means engaging said cam means operatessaid box stopping means.
 20. The box flapper of claim 19 wherein saidbox stopping means includes a pair of spring-loaded wedges engaging andriding along opposite sides of said succeeding box and for springinginward to stop said following box when the trailing end of saidsucceeding box moves past said wedge means.
 21. The box flapper of claim20 wherein said flap engaging means includes both leading and trailingrollers oriented on each end of said arm relative to the direction ofrotation of said arm so that leading rollers engage and open saidleading transverse flap of said one box and trailing rollers engage andopen said trailing transverse flap of said one box.